San Diego County sheriff's officials confirmed Monday the 16-year-old Lakeside teenager was held against her will.

"It's clear from the information that we received that she was under extreme duress. She was taken out of the county, out of the state, clearly against her will," Sheriff Bill Gore said.

The sheriff has scheduled a 2:30 p.m. update. NBC 7.com will cover the news conference live.

While FBI agents conduct an investigation into the shooting that killed the 40-year-old DiMaggio, a spokesperson described how federal agents moved in on the Boulevard man and his kidnap victim Hannah Anderson.

After days of searching, U.S. Marshals spotted a tent from the air near Morehead Lake on Saturday afternoon.

Pack said the team had to hike with up to 100 pounds of tactical gear along a rough trail characterized by steep switchbacks and treacherous footing.

The teams then surrounded the camp and waited until Anderson and DiMaggio were no longer near each other before moving in, and ultimately killing DiMaggio.

“They had a very good idea from everything they could see from the air that this in fact was Hannah and DiMaggio there on the ground,” said Ada County Sheriff's Office PIO Andrea Dearden. “They waited until the two were separate, ensuring Hannah's safety, and that's when they moved in to make that rescue.”

Sheriff Gore told a local television station Monday that after debriefing, agents said DiMaggio did have a shoulder weapon and fired at least one shot.

Few other details about the shooting are being released pending an automatic investigation by FBI agents of everything that occurred before, during and after the shooting.

Sheriff Gore said it was apparent in the debriefing that Hannah Anderson was not aware her mother and brother had been killed.

"We'll be putting the pieces together from what we found out in Idaho, from the interview of Hannah. We'll be putting that together with the physical evidence we found at the scene from where the murders occurred, the fire. And putting it all together," Gore said.

San Diego area law enforcement expert Alan Poleszak told NBC7 while the FBI obviously would have liked to determine DiMaggio’s motive, bringing Hannah home was priority number one.

Poleszak spent 24 years in the Drug Enforcement Administration (DEA) and worked closely with his counterparts in the FBI.

FBI agents are trained for specific action and reaction, and to resolve a threat as soon as it presents itself Poleszak said.

“It's a very fluid, dangerous situation,” he explained adding that lethal force is always viewed as the last resort but sometimes it's the only option.

“They must have determined at some point during the case that DiMaggio posed an imminent threat to that child or the agents trying to arrest him and rescue Hannah, and at that point they determined the use of lethal force was necessary to protect against serious bodily injury or harm to that child or the agents,” Poleszak said.

He says agents had to consider multiple scenarios and then act in an instant “either to prevent access to means to harm the child or the agents, or he already had access to means, or he was utilizing means and effectively acting a threat.”